This invention relates to foam blowing agent blends of 1-chloro-1,1-difluoroethane ("142b") and 2-chloro-1,1,1,2-tetrafluoroethane ("124b"), more particularly to nonflammable blends containing up to about 70 weight % of 142b and at least about 30 weight % of 124, and to nonflammable premixes and polyurethane foam compositions containing such blends.
Until now, 142b has often been listed in patents as a potential polyurethane foam blowing agent, but its use has usually been dismissed because of its known flammability. However, with the anticipated phase-out of the leading commercial foam blowing agent, 1,1-dichloro-1-fluoroethane ("141b"), the marketplace has a need for other foam blowing agent alternatives.